In past years, as handheld electronic devices became smaller, it is desired to downsize antennas used in handheld electronic devices, e.g. mobile phones, notebooks, access points (AP) or wireless transmitting devices. The developed antennas are operable for the IEEE 802.11 standard including 802.11a operating in the 5-GHz band, and 802.11b and 802.11g operating in the 2.4-GHz band.
Monopole antennas and planar inverse-F antennas (PIFA) are two of the most widely-used antennas in handheld electronic devices. Please refer to FIG. 1, which is a diagram showing a conventional PIFA. In FIG. 1, the inverse-F antenna 10 includes a ground terminal 101, a first radiator 102, a second radiator 103 and a long side L1. The first radiator 102 and the second radiator 103 are used to radiate electromagnetic wave signals in different frequency ranges. Because the inverse-F antenna 10 includes the ground terminal 101, it is easy to adjust its impedance matching. In addition, the inverse-F antenna 10 is commonly used in modern handheld electronic devices because they are advantageous in their simplicity in structure and have good transmission performance.
Monopole antennas are half the size of their dipole counterparts, and hence are attractive when a smaller antenna is needed. Although monopole antennas have a smaller size than the inverse-F antennas because no ground terminal is required, but monopole antennas have a disadvantage of less adjustable variants and thus less flexibility in the matching adjustment due to the lack of the ground terminal. In addition, the conventional antennas, such as PIFA, are usually made of iron sheets, and the signals thereof are usually fed by cables, which may cause high cost for die and iron materials.
To overcome these problems, a novel dual-band printed monopole antenna is disclosed in the present disclosure after a great deal of research, analysis and experiments by the inventors.